front tires don't spin in 4wd

front diff actuator functions good
but my front tires in 4wd have no power any ideas

 

Does the front driveshaft spin when in 4wd? That will tell you if the transfer case is working.

 

just put a new used transfer case on it and it spins driveshaft

 

Then somehow the front actuator isn’t doing its job if it’s functioning. Could be something internal to the differential itself.

Out of my zone of expertise.

 

Sounds like your front actuator...

https://www.tundras.com/threads/1st-gen-4wd-issues-diagnosis-prevention-guide.149189/

 

Have you jacked the truck up and verified neither wheels are spinning when the truck is in 4WD? If you're stuck in 4WD, the differential will only send power to one wheel because it is an open differential. This is what people refer to as one wheel peel. Since the front differential is open, the front wheels spin independently. The wheel with the least amount of resistance/ traction will spin while the other is freewheeling.

You will have to disconnect the rear driveshaft from the transfer case if you jack the front of the truck up to test whether your front wheels turn in 4WD.

 

Could one jack up the entire truck....all four wheels off the ground....to test that?

(Having 4 shop jacks is pretty nice, I admit).

 

Yes, a few different ways to test this sort of thing for sure. You could also completely uninstall the rear driveshaft from both the transfer case and the rear differential, effectively turning your truck into a front wheel drive vehicle when you have 4WD engaged (truck doesn't move in 2WD with the rear driveshaft removed obviously). The output shaft and companion flange on your transfer case that the rear driveshaft bolts to still spins at the same speed as as the front driveshaft on the transfer case (again, with no rear drive shaft, think of a PTO on a tractor that's spinning but not connected to a tool).

Probably the safest to remove the rear driveshaft honestly instead of using jackstands.If the truck isn't moving in 4WD with the rear driveshaft removed, but your front driveshaft is spinning, you'll be able to tell if the front differential is sending power to the CV axles. If there is no power to either of the CV axles, but the driveshaft is spinning, there's something wrong with the differential internally usually. If the internals are fine in the differential, there could be something wrong with the joints inside the CV axle or the outboard wheel bearings, but that would be pretty noisy.

 

Or simply put the truck in 4 wheel drive and drive in a tight circle. For the sake of the driveline do this in gravel or other low traction surface. You're going to feel it bind and break lose repeatedly while going around the circle.

 

Yep, 1000% agree with this as well. But in the case of OP or whoever else that wants to try and diagnose these problems and doesn't fully understand the binding and what that feeling entails, my last reply is where I'd start with trying to isolate the exact issue.

 

Jeez man, I hope you can get this rectified. Having 4 wheel drive and not having 4 wheel drive sucks!!

 

I’ve put all 4 wheels on jackstands and let the truck coast in 4wd. I recall seeing one wheel in front and one wheel in back slowly moving.

Just remember to climb back in and put your foot on the brake to shift it into park from drive. I made the stupid mistake of just shifting it into park standing outside the truck and could hear the banging of the parking pawl slow down the wheels to a stop. I’m sure that put some unwanted wear on it.

 

Yep, I did that once with an S10 Blazer. Didn't hurt that thing though. They were freaking bullet and Marine proof!! Ask me how I know.

 

If the driveshaft is spinning and the actuator is working and completing the 4wd shift with the light illuminating solid, then sounds like you possibly have an issue inside the front diff. I'd guess it's the input gear on the actuator side. It necks down really small where it goes into the spider gear and is probably the weakest part of the diff. I've broken one in the past offroading on 32" tires. The little 7.5" 4cylinder diff is not very strong under a 4.7 tundra.

 

I don't actually use jackstands, I block up on 6x6's and 4x4's. I just feel those are less likely to tip over.